The present invention relates to polymer processing systems and methods for using same. More particularly, the invention relates to polymer processing systems including decompression chambers preferably structured to provide products which are more aesthetically pleasing, and methods for using such systems.
Polymer processing to produce articles, such as sheets, films, other profiles and the like, has become increasingly important as the use of such articles become more prevalent. Production of polymer products often involves the use of extrusion processing, for example, using screw extruders, other types of extruders and the like, to produce a workable or flowable extruded polymeric material. This extruded polymeric material is often passed through a die configured to produce a polymer product of a desired shape or configuration from the extruded polymeric material.
One disadvantage of such processing is the presence of visually apparent markings, blemishes and the like, such as extrusion marks or markings, in the final product. Such markings and the like are the result of processing in the extrusion assemblies, e.g., the extruder or extruders in which the extruded polymeric material is produced. Because the polymeric material leaving the extrusion assembly is under a substantial degree of stress resulting from work done on the material in the extruder, extrusion markings are produced on this material leaving the extruder. Since the die assembly is often substantially adjacent the extruder or extruders, the extrusion markings often are present in the final shaped polymer product from the die assembly. Such extrusion markings in the final product is aesthetically disadvantageous, may reduce the value of the product and may be so severe as to require expensive reprocessing.
Various approaches have been suggested to avoid such extrusion markings. For example, the production rate of a product can be reduced to allow for less stress to be placed on the polymeric material being passed through the extruder or extruders. Alternatively, or in addition, the distance between the extruder or extruders and the die assembly can be lengthened to allow the extruded polymer material more time before final shaping so that the extrusion markings may become less apparent. However, such approaches reduce production rates and/or increase production costs. In addition, providing longer distances between the extruder(s) and die assembly can be disadvantageous in that polymeric material can hang up within, or even block, the processing system, which can result in system shutdown, leading to substantial additional costs and system downtime.
There continues to be a need for polymer processing systems which reduce extrusion markings in the final shaped polymeric products while, at the same time, avoiding reduced production rates and increased costs.